Ocado's shares are continuing their slide following its disappointing first half update this week, with joint broker Goldman Sachs adding to the misery by cutting its recommendation from buy to neutral.

The online grocer said on Tuesday its trade had been disrupted by the Jubilee celebrations and it was uncertain what effect the forthcoming London Olympics would have. Analysts raised concerns about its financial position and its investment in a second warehouse, while competition continues to increase, including from its main supplier Waitrose and Tesco's move to increase its Click and Collect service. Many in the industry believe a standalone online operation is at a disadvantage without a physical store to help defray costs.

Now Goldman has issued a negative note, reducing its six month price target from 140p to 110p. The bank's analyst Karen Hooi said:

We downgrade Ocado and revise our estimates and price target following the first half . Since upgrading Ocado to buy on 1 March 2011, the shares are down 60.2% versus our Europe Small & Mid Cap universe. We believe the underperformance is due to continued concerns on Ocado's capacity expansion capability and the potential impact from rising competition on its revenue growth.

Having started the week at 107.3p, Ocado's shares have fallen another 4.85p to 74.65p, the biggest faller in the mid-cap index.

This is bad news for new finance director Duncan Tatton-Brown, who bought 50,000 shares on Tuesday at 98.91p each. His wife Kate bought the same amount at 99.57p. At the moment they are sitting on a loss of more than £24,500 between them.